Conventional scintillator materials excel at detecting incident radiation of various types according to predetermined characteristics of the material and/or radiation, notably including spectral band (wavelength) of the incident radiation. The scintillator material absorbs the radiation, generating a scintillation event, which emits light into the scintillator material. Preferably, the light is emitted in the direction of a detector coupled to the scintillator material, such as a photomultiplier, which converts the photon to electrical potential, generating an observable signal. However, there is an element of randomness to the direction in which light is emitted from the scintillation event. While most light emitted from the scintillator typically undergoes total internal reflection (TIR), i.e. reflection with 100% efficiency, and therefore reaches the photomultiplier, in conventional arrangements some light loss is experienced, reducing the scintillator sensitivity and resolution.
For example, if the light is emitted in a particular range of angles close to a direction normal to the orientation of the scintillator material surface (also known as an “escape cone”), upon reaching the scintillator-air interface, the light will escape the scintillator material rather than undergoing TIR and reaching the photomultiplier. Similarly, light traversing the scintillator material may undergo backscattering events, e.g. upon light encountering an inclusion or impurity in the scintillator material. Backscatter events introduce another opportunity for light to be emitted in a direction that would result in escape and ultimate signal loss.
In an attempt to improve the sensitivity and resolution of scintillator materials by reducing losses such as those described above, some groups have employed reflective scattering approaches, such as can be achieved by wrapping a scintillator material in a reflective tape (such as Teflon). These reflective wrapping techniques beneficially reduce the amount of light that escapes form the scintillator material, but since the reflective wrappings operate by scattering light without any significant directional guidance, light propagation is inefficient, which can also cause undesirable signal losses.
Other attempts to solve the signal loss problems described above have employed metallic layers, for example aluminum having a high reflectance coefficient, typically about 90%, to reflect escaping light back into a scintillator material. However, while the metals have high reflectance coefficients, signal is still lost with each reflectance event, ultimately causing unacceptable signal loss over a potentially large number of events in a given experiment. For example, assuming a 90% reflectance coefficient, the scintillator-metal arrangement would lose 10% at each reflectance event, which translates to a loss of half of the original signal with merely 10 events. As will be appreciated by one having ordinary skill in the art, this fact is severely limiting on the size and therefore suitability for various applications, of the underlying scintillator material.
Accordingly, it would be beneficial to provide systems and methods for improving scintillator sensitivity and resolution by reducing signal losses without suffering from the drawbacks associated with reflective wrapping and metal mirrors currently in use to address the problem of signal loss.